CHAPTER 4 DISCUSSION
4.3. RESULTS OF TREATMENT OF DME BY PHOTOCOAGULATION LASER 1. Results on BCVA
BCVA improvement was most pronounced after 1-6 months, decreasing from 9-12 months.
This can be explained by the progressive cataract. Cataract in patients with diabetes are common complications. Complications of cataract was found in laser treatment, especially retinal scatter laser. Tunç see the highest vision improved in 18 weeks after treatment.
Regarding the focal DME group, BCVA improves ≥ 5 letters after 1 month 56%. This positive result compared to the rest can match, and after 12 months was 46.4%. Compared with the results of RESTORE study, no improvement in visual acuity consistent focal group treated with laser alone. Probably due to the selection of initial patient subgroups, the authors did not choose in this subgroup of eyes with low vision, resulted in improved visual acuity less.
In particular, the group of diffuse and cystoid DME, best improvement on BCVA at 6th months, up to 52% of eyes, while the 12nd month, BCVA improved at least 36% of eyes.
Notably, increased acuity of eyes with little or no increase in this group is high, accounting for 68% after the first month, 52% after the first month 3.48% after 6 months, 60% after 9 months and 64% after 12 months. Consistent BCVA of local DME group improved compared with the
other groups. Visual acuity improved ≥ 5 letters accounted for 56% in the first month, 54.8% at 3rd month, 53.6% at 6th month, 50% at 9th months and 46.4% at 12nd months.
In studies of diffuse macular edema of Lam, there is no improvement in sight at all times to monitor the laser treatment alone grid, while the combination of laser eye treatment with intraocular triamcinolone injections, BCVA has increased slightly in week 2, 4 and 9 than before treatment.
Our successful outcome compared with the previous authors, is explained by the study subjects selected at an earlier stage, partly due to the treatment of diabetes has made progress, causing little damage secondary or natural progression of diabetic retinopathy.
In the ETDRS, because the purpose is to maintain eyesight, with 43 % of eyes with BCVA ≥ 20/25, 41% of eye with BCVA in about 20/50 - 20/25, only 16% of eyes haves BCVA < 20/50, the results show that the emphasis in maintaining visual acuity in 50% of eyes, the degree of improvement compared with our study is not high at first glance but can be interpreted as due to weak factors vision before treatment was also high.
In the RESTORE study, consistent with local DME subgroup, mean BCVA improved after 12 months of treatment with laser alone (52 eyes) is not satisfactory, less than 5 letters (ETDRS).
In accordance diffuse DME subgroup, grid laser treatment also resulted similary in improved BCVA (0 ETDRS letters)
In laser treatment arms of the BOLT study, 5.3% of eyes achieving ≥ 15 letters increase, with 7.9% increase over 10 letters. The result is better than the RESTORE study, but slightly lower than in our study (11.9 and 11%).
With the results of the READ2 study, 3.6% of eyes achieved results increases ≥ 15 letters after laser 6 months and 24 months is 2.9%. If we increase the number of eyes achieving ≥ 5 letters, after 24 months was 47%, close to the results of our study. READ2 Research has shown that laser treatment results over time superior to treatment with intraocular injection ranibizumab.
In the DRCR – Net study, the follow-up period of 2-3 years, shows with laser treatment alone, in the first year to 15% of the eye results have improved vision ≥ 15 letters, after 2 years is 18%, after 3 years of improving eye vision was 44% ≥ 10 letters.
Research Da Vincy follow-up for 52 weeks, showed that at 24 weeks, improve eye vision of
≥ 10 letters after laser treatment was 32 %, 21% ≥ 15 letters. This result is higher than in our study, after 6 months of treatment results was 24.7% respectively and 11.9%.
In some other studies of laser, showing the general trend is to avoid complications due to macular edema, with 50 -80% of the eyes to maintain eyesight.
4.3.2. Results of CRT mesured by OCT
With technical diagnosis for macular edema by OCT, can detect changes central retinal thickness to 5 µm. Given the relatively stable macular edema, retinal order to reduce swelling in the short time of 30 µm is rare, so the observed change central retinal thickness on OCT with high value of sensitivity. Shortly after 1 month of treatment, may see the central retinal thickness reduction of 50 µm.
Local DME group in line with results close to the average value of 276.36 ± 20.86 μm (the average value of the central retina measured by OCT was 256 μm). This is the ideal results in the treatment of macular edema, hoping macular region of the retina taken back to the state close to the normal anatomy.
From 9thmonth to 12nd month, the CRT measured by OCT in both groups almost unchanged, which suggests that treatment results reduce swelling of the retina was stable after 9 months.
There are 5 eyes in the study retinal thickness decreased compared with normal parameters, the following follow-up period of 12 months. It can be hypothesized that the progressive retinal atrophy in the eye macular edema with chronic prolonged. This observation was also made by other authors Lam DS that advanced age is also a factor causing retinal atrophy.
4.3.3. Laser complications
Although retinal laser technique is relatively safe, but the technique is not entirely harmless.
Complication common is corneal epithelium erosion in patients with diabetes in general.
Can explain the characteristics of corneal epithelium vulnerability of people with diabetes, because structural changes basement membrane and epithelial cell morphology, leading to easy peeling corneal epithelium, especially under the influence use of anesthetic eyedrops and impact on the ocular surface.
Complications after laser such eye pain without corneal accounted for no more, only 12 cases. Soreness will go away after resting, explain, investigate artificial tears that no case shall analgesia. This complication or referred to in the literature, can be stimulated ciliary putting contact lenses for laser.
No other serious complications encountered while working as touching laser foveola, vitreo – retinal hemorrhage.
4.3.4. The correlation between BCVA and CRT changing
Through evaluating the variable r, the correlation between improving visual acuity and reduced central retinal thickness mesured by OCT are not closely related, the highest at the start of the study r = 0.341. This result is similar to the study of Hee with r = 0.45.
This suggests evaluating of treatment outcome remains to be based on the level of visual improvement, results based on measured central retinal thickness on OCT for reference.
4.3.5. Laser parameters and additional treatment
Indication for additional laser if results after 3 months of increased visual acuity < 5 letters, lesions in the macula of the retina does not shrink or even develop, in addition to reference results as central retinal thickness have not increased. The laser additional 3 months, in order to avoid the next time the laser sting insect bites in advance, thereby preventing complications choroidal neovascularization. If 6 months after 2nd treatment results will not reach a conclusion as treatment failures.
Some other authors based on changes in retinal thickness measured by OCT as the central criterion for additional laser treatment immediately. In the study PKC - DMES Study Group, the author sets the standard when the central retinal thickness measured by OCT increased from 100 micrometers or more need additional laser treatment immediately.
Meanwhile, additional standards for laser research is ETDRS appear newer leakages around the macula (3000 micrometers from the center point).
About laser treatment parameters, our study uses start laser energy is higher than of the ETDRS Research and Olk (50 mW compared to 10 mW). May be the lasers we use the 532 nm laser, laser parameters different from other authors using argon or krypton laser. However, the our average energy lower than most other authors. In modified grid laser, grid laser shoots of
ours and Olk are similar but much less than the number of shoots in the ETDRS standard procedure. Reduced number of shoots by not covering all around the macula, which focused on the edema area of retina.
The advantage of this method is not only reduces chorio- retinal damage, but also preserve the nerve fiber bundles papilledema - macula. Number of shoots in focal laser in turn depends on the specific circumstances, some regions of the aneurysm with the size of the detector and service hard exudates.
CONCLUSIONS 1. Clinical feature of diabetic macular edema
- 77,1% of eyes with local form of diabetic macular edema (84/109 eyes), 6,4% of eyes with cystoid form (7/109 eyes) and 16,5% of eyes with diffuse form (18/109 eyes).
- 70,3% of patient who have bilateral diabetic macular edema (45/64 patients); 29,7%
unilateral (19/64 patients).
- 2,4% of eyes with excellent VA (visual acuity) – ≥20/25 (2/109 eyes), only in local form group. 30.3% of eyes with good VA (from 20/50 to under 20/25) (33/109 eyes). 67,9% of eyes with poor VA (under 20/50) (74/109 eyes).
- Retinal central thickness (RCT) measured by OCT is 345 ± 57,69 µm per average, RCT in group of cystoid form and diffuse form is 403,52 ± 61,27 µm, RCT in group of local form is 327,58 ± 43,66 µm per average.